Process for packaging highly viscous tacky materials

ABSTRACT

A process for packaging viscous tacky polymers which comprises hot filling a container with the polymer wherein the container has a liner comprising (1) heat-stabilized nylon coated with a silicone release agent; (2) an uncoated cellophane film; (3) a mineral pigment coated kraft paper overcoated with a silicone release agent; or (4) kraft paper coated with finely divided mica.

United States Patent Higgins et al.

PROCESS FOR PACKAGING HIGHLY VISCOUS TACKY MATERIALS Inventors: John J. Higgins; Nova E. Stucker, both of Westfield, NJ.

Assignee: Esso Research and Engineering Company, Linden, NJ.

Filed: Mar, 28, 1972 Appl. No: 238,856

Related Us. Application Data Division of Ser. No. 42,985, June 3, 1970, which is a continuation-in-part of Ser. No. 676,097, Oct. 18, 1967, Pat. No 3,545,643.

US. Cl 141/1, 53/5, 220/63,

220/63;64 Int. Cl B65b 3/04 Field of Search 206/84; 141/1; 117/76 F,

1 1 Sept. 24, 1974 [56] References Cited UNITED STATES PATENTS 3,648,882 3/1972 Shelton 206/84 FOREIGN PATENTS OR APPLICATIONS 883,069 ll/l96l Great Britain Primary ExaminerHouston S. Bell, Jr.

[5 7 ABSTRACT A process for packaging viscous tacky polymers which comprises hot filling a container with the polymer wherein the container has a liner comprising (1) heatstabilized nylon coated with a silicone release agent; (2) an uncoated cellophane film; (3) a mineral pigment coated kraft paper overcoated with a silicone release agent; or (4) kraft paper coated with finely divided mica.

8 Claims, 1 Drawing Figure PROCESS FOR PACKAGING HIGHLY VISCOUS TACKY MATERIALS CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of US. Patent application Ser. No. 42,985 filed June 3, 1970, which is in turn a continuation in part of application Ser. No. 676,097 filed Oct. 18, 1967, now US. Pat. No. 3,545,643.

BACKGROUND OF INVENTION Most highly viscous tacky polymers such as low molecular weight polyisobutylene are mixed and packaged hot," e.g. greater than 250F., so that the material will flow to some extent or at least be pourable. Containers for these type materials must be able to withstand the hot packaging temperatures of approximately 300 to 450F. and at the same time permit the contents to be readily removed for final use.

These materials are presently packaged in expensive metal containers which are much lighter weight than is desired for the product protection and durability since the container must be peeled from the product in use. These containers are generally coated with a release coat which must be manually applied after the can is manufactured and is therefore generally of poor quality.

SUMMARY OF THE INVENTION It has now been found that low molecular weight tacky polymers may be readily removed from their containers by providing the container with a removable release agent coated inner liner. A particularly advantageous inner liner material is heat stabilized nylon coated with a silicone release agent.

BRIEF DESCRIPTION OF DRAWING The various objectives and features of the invention will be fully understood by reference to the accompanyin g drawing which is an expanded view of a container having two removable ends and an inserted lining, the lining extending out beyond the edges of the container body and being folded back over said edges.

DETAILED DESCRIPTION The container of this invention is suitable for use for such tacky polymers as polyisobutylene having a Staudinger molecular weight of 8,000 to 12,000, polybutenes having Staudinger molecular weights of about 3,000 to 6,000, low molecular weight butyl rubbers and halogenated butyl rubbers and like compounds which are normally not pourable at room temperature, but exhibit cold flow at room temperature and are sufficiently tacky to be removed from conventional containers only with difficulty.

The inner liner should be capable of withstanding hot packaging conditions without degradation or softening to the point of adhering to the polymer being packaged. Various polymeric films have been found to be useful for this purpose. Typical of the types of film which may be used are polyester films and heat stabilized nylon. Preferably, the polymeric film has a thickness of about 0.5 to about 5 mils; more preferably about I to about 3 mils.

A particularly suitable polyester film is the reaction product of ethylene glycol and terephthalic acid which is known to the trade by the duPont trandemark Mylar.

The term nylon as used in the specification and claims is used in its generic sense to mean long chain synthetic polyamides which have recurring amide groups. Illustrative examples of nylons suitable for use in the practice of this invention are nylon 4 prepared from pyrrolidone; nylon 66 prepared from condensation of hexamethylenediamine with adipic acid; nylon 610 obtained from the condensation of hexamethylenediamine with sebacic acid; nylon 6 obtained by polycondensation of caprolactam; etc. Aromatic polyamides are particularly well suited for use in the practice of this invention due to their excellent thermal properties.

Though any nylon may be used as a container liner when coated with a silicone release agent, it is preferable that where packaging is carried out at elevated temperatures, e.g. 300450F., the nylon be a heat stabilized nylon.

With the exception of aromatic polyamides, conventional nylons tend to become embrittled at temperatures above 350F., especially above 400F., e.g. 450-440F. Hence, at these elevated temperatures, it is essentially, i.e., above 350F., necessary that the nylon be heat stabilized nylon. The term heat stabilized nylon" as used in the specification and claims refers to nylons which are stable against heat embrittlement at temperatures of about 350-450F.; particularly at temperatures of 400-450F., the temperature at which tacky polymers are often packaged.

Heat stabilized nylons are well known in the art and are generally prepared by the addition of specific oxidation stabilizers and/or heat treatment of the nylon film. Particularly preferred are the nylons prepared from a C monomer, i.e., nylon 6. Illustrative of such heat stabilized nylon films is Allied Chemicals Capran 80, which has the following physical properties: at 72F., tensile strength of 10,000-l4,000 psi, yield strength of 5,000-8,000 psi, tear strength of -100 gms., elongation of 400-600 percent, negligible solubility in water, crystalline melting point of 424-428F.; at 300F., tensile strength of 6,000-7,000 psi, yield strength of 2,500-2,700 psi, and elongation of 400-500 percent.

Illustrative of aromatic polyamides is duPonts Nomex. The term aromatic polyamides" as used in the specification and claims means a polyamide which contains a repeating phenylene group in the polyamide backbone. Preferably, the phenylene group is a paraphenylene. The structure of such polyamides is broadly described by the general formulae:

poly (m-phenylene isophthalamide) TCWQCWNEQWHJL and The term film as used in the specification and claims includes polymeric papers such as Nomex paper. These products are generally produced on conventional paper making machines from two different forms of the same polymer: short fibers (floc) and smaller fibrous broader particles (fibrids). After processing on conventional paper making equipment, these two constituents are permanently bonded together by heat and pressure.

In order that the polymeric films release properly from the packaged polymer, it is necessary to coat the film with a release agent. Various release agents may be used in the practice of this invention. Preferably, the release agents are silicone fluids having a viscosity of about to about 30,000 centistrokes at 77F preferably about 50 to 1,000 centistokes, most preferably 100 to 500 centistokes. The materials are well known to the art having carbon to silicon linkages such as disclosed in US. Pat. Nos. 2,448,756, 2,484,595 and 2,541,137 which are incorporated herein by reference. These polymers have the general structure:

wherein R, and R are selected independently from methyl and hydrogen wherein either R, or R is methyl and the other is methyl or hydrogen. Where both R, and R are methyl, the fluids are known as dimethyl silicones or dimethyl siloxanes. The hydrogen attached to the silicon is termed a silanic hydrogen.

The silicone fluids of this invention may, if desired, be cured after application to the polymeric film. The fluids may be applied as the neat oil or from a solvent solution. The solvent may be C -C alkanes such as hexane, heptane or 2-ethyl hexane, C to C aromatics such as benzene, toluene or xylene or any of the well known chlorinated solvents such as methylene chloride or chlorobenzene. Generally, the silicone fluid is present in the solvent at about 30 wt. percent.

Where either R, or R of the silicone fluid is hydrogen, that is a methyl silicone having silanic hydrogens, the fluid is moisture curable below 50C. in the pres; ence of a catalyst such as disbutyl tin dilaurate, or dibutyl tin di-2-ethyl hexoate. High temperature cures are accomplished in the presence of catalysts such as zinc octoate.

Where both R, and R are methyl, the fluid may be moisture cured by the addition of a silanol and a catalyst such as an organic titanate, e.g. tetra-isobutyl titanate and tetra-Z-ethylhexyl titanate.

The dimethyl silicones are also available as hydroxy terminated polymers which may be cured in the presence of organic titanates without the addition of silanols to the polymer.

Illustrative of the dimethyl silicones are Union Carbide and Carbons L-45 series fluids and General Electric Co.s SF 96 series fluids, both products being available in a wide range of viscosities up to about 100,000 cs at 77F. Illustrative of silicone fluids having silanic hydrogens are Union Carbide and Carbons L-3l, a silicone fluid having a viscosity of about 35 cs at 77F and Y-4006 fluids and Dow Cornings Dow Corning 23 silicone fluid. The Y-4006 and Dow Corning 23 fluids are supplied as 30 wt. percent neat oil in xylene. Illustrative of the hydroxy terminated dimethyl silicones are Union Carbide and Carbons W-900 and Y-l,480.

It has been found that the thickness of the release agent coating is not critical. However, it is essential that the coating be continuous. For example, a continuous coating whose thickness is in the Angstrom range will suffice, whereas a discontinuous coating of several mils will not release properly.

Though many coated release papers are available on the market, such as silicone coated glassine, silicone coated parchment and silicone coated latex treated stock, and are effective as release surfaces, they are not generally suited for use in the practice of this invention since they become excessively embrittled by the heat history of hot packaging and can be removed only in small pieces.

Surprisingly, it has been found that uncoated cellophane is a satisfactory release surface for the purpose ofthis invention. It is not embrittled by packaging heat history and may be removed from the packaged polymer without the aid of a release agent.

the cellophane may be removed from the packaged polymer by wetting with water. The water breaks the bond between the polymer and the cellophane, and the cellophane, having sufficient cohesive strength, is removed in one piece. Preferably, the cellophane film is about 0.5 to about 5 mils in thickness, more preferably about I to about 3 mils.

In order to be suitable for use in the practice of this invention, the cellophane should not be coated with any substance designed to make it waterproof or to limit the penetration of water or water vapor through the cellophane. The term uncoated cellophane as used in the specification and claims means cellophane which has not been so coated.

The term cellophane as used in this specification and claims means films produced from wood pulp by the viscose process, known in the trade as uncoated type cellophanes.

Illustrative of suitable cellophane films are the cellophanes known to the trade as type PD, type PUD and type PUD-O cellophanes which are available from E. I. duPont de Nemours and Co.

Although other release papers have been found to be not generally suitable for use in the practice of this invention, it has suprisingly been found that kraft paper having a basic weight of at least 30 lbs./ 1,000 ft. coated with finely divided mica, is a suitable release surface for the purposes of this invention. Preferably, the mica coated kraft paper has a basic weight of about 50 to about 100 lbs/1,000 ft.

The finely divided mica should have a platelet shape with a thickness of about to about 200 Angstroms and about 100 times thickness in diameter. Preferably, the mica is a synthetic mica. Synthetic mica is a fluorine derivative of phlogopite made by treating potassium fluorosilicates with alumina under pressure and heat or by melting basic oxides, fluorides and feldspar together.

Illustrative of the synthetic mica coatings which may be used is a product known in the trade by the Minnesota Mining & Manufacturing Co. trademark Burnil Brand Microplates. Burnil Brand Microplates are extremely thin platelets of synthetic mica. The average particle size is about 20-100 Angstroms in thickness and about 100 times thickness in diameter. The platelets have a melting point of l,800F., a density of 2.7 g./cc. and a refractive index of 1.5.

Mineral'pigment coated kraft paper which has been coated with the silicone release agents of this invention are also suitable for use as release surfaces. The coated kraft paper should have a basic weight of at least lbs./ 1,000 ft; preferably about 50 to about 100,

lbs/1,000 ft.*.

The term mineral pigment as used in the specification and claims means water insoluble, inert inorganic compounds. The mineral pigments are generally finely divided and deposited on the kraft paper from a slurry or by direct deposition of the powder prior to a calendering step in the preparation of the paper. Illustrative examples of mineral pigments are clay, talc and calcium carbonate. Preferably, the mineral pigment is clay.

The mineral coating is an essential part of the composition since if the kraft paper is not so coated, it is ineffective as a release paper at elevated temperatures even when coated with silicone release agents.

The term container as used throughout this specification is intended to mean any suitable container having vertical side walls and at least one end which can be removed or opened. Illustrative of the container materials which may be used are fiber board, corrugated boxes, metal drums and the like.

In one embodiment of this invention, a covered metal can may be supplied with a Mylar bag internally coated with a silicone release agent, the release agent coated Mylar bag being placed into the container and filled with the tacky polymer. The top of the bag is then tied and the cover put in place. When the polymer is ready for use the container is opened, the inner bag and contents removed from the container and the polymer is stripped of the Mylar bag.

In its preferred embodiment, shown in the drawing, the container comprises a cylindrically shaped body, 1, having two removable ends, 2, 3, equipped with an inner liner release surface, 4. The removable ends are preferably of metal and coated with a silicone release agent. The inner liner release surface is formed in the shape of a cylinder and several inches longer in length than the container itself, e.g. 3 to 4 inches longer. Preferably, the inner liner is a silicone coated heat stabilized nylon. The container body, 1, itself must be smooth walled and have no inner lips. The cylindrically formed inner liner, 4, is inserted into the cylindrical container body, 1, and folded back, 5, over the container edges, 6. One removable cylinder end is put in place. The container is then filled with polymer and the remaining removable end put in place and sealed by means of tape, plastic or metal straps and the like.

It is readily evident from the above description that the need for a separate container liner may be obviated by constructing the container of heavy kraft paper (e. g. 200 lbs/1,000 ft?) which has been coated with synthetic mica. The container may be readily cut away to remove the contents. For example, conventional fiber drums may be made having their inner surface coated with synthetic mica. Preferably, the coating will be accomplished prior to construction of the drum. If desired, the mica may be applied to a finished drum by slush coating using a slurry of synthetic mica having about 5 to about'25 wt. percent solids.

Alternately, a light weight (i.e., 50-100 lbs./ 1,000 ft?) mineral pigment coated kraft paper with an overcoat of silicone release agent may be glued to the inside of the fiber drum after it has been rolled and removed from the mandrel during manufacture.

The weight of the drum wall will be a function of the size of the container using conventional shipping guidelines. For example, a 15 gallon fiber drum having a l 15 lbs. net weight limit would be constructed of a five ply kraft paper wall having a bursting strength of 500 lbs.

While the foregoing description and accompanying drawing illustrate a preferred manner of employing this invention, many different embodiments may be made without departing from the spirit and scope thereof and it is to be understood that the present invention is not limited to the specifically disclosed examples thereof.

What is claimed is:

1. In a process for packaging tacky polymers which comprise pouring the polymer into a container at a temperature at which the polymer is free flowing, the improvement which comprises lining said container with an inner liner selected from the group consisting of l) a polymeric film wherein said film is heat stabilized nylon or a polyester film which is the reaction product of ethylene glycol and terephthalic acid, said liner being coated internally with a continuous film of a silicone release agent selected from the group consisting of dimethyl silicones, methyl silicones containing silanic hydrogens and hydroxy-terminated dimethyl silicones, wherein said silicone has a viscosity at 77F. of about 10 to about 30,000 centistokes; (2) a kraft paper having a basic weight of at least 30 lbs/1,000 ft said paper being coated with a finely divided mica; (3) a paper release surface comprising a kraft paper having matic polyamide.

5. The process of claim 4 wherein the polyamide contains repeating para-phenylene groups in the polyamide backbone.

6. The process of claim 1 wherein the silicone release agent has a viscosity of about 50 to about 1,000 cs.

7. The process of claim 6 wherein the release agent viscosity is about to 500 cs. 

2. The process of claim 1 wherein the silicone release Agent is cured after application to the film.
 3. The process of claim 1 wherein the heat-stable nylon is heat stabilized polycaprolactam.
 4. The process of claim 1 wherein the nylon is an aromatic polyamide.
 5. The process of claim 4 wherein the polyamide contains repeating para-phenylene groups in the polyamide backbone.
 6. The process of claim 1 wherein the silicone release agent has a viscosity of about 50 to about 1,000 cs.
 7. The process of claim 6 wherein the release agent viscosity is about 100 to 500 cs.
 8. The process of claim 7 wherein the release agent viscosity is about 100 to 500 cs. 